Reduced-pressure drying unit and coating film forming method

ABSTRACT

The invention includes a hermetic container provided with a substrate mount; a vacuum exhauster connected to the hermetic container; a current member; and a current member raising and lowering mechanism. When the current member is raised and lowered as a function of the pressure inside the hermetic container, a liquid flow of the coating solution on the substrate is controlled, thereby controlling the uniformity of the film thickness of the coating solution.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a reduced-pressure drying unit and acoating film forming method for vaporizing a solvent from a coatingsolution when the coating solution made by, for example, mixing acomponent of a coating film in the solvent, for example, a resistsolution is applied to a substrate such as a semiconductor wafer or anLCD substrate (a glass substrate for a liquid crystal display) to formthe coating film.

2. Description of the Related Art

In fabrication processes of semiconductor devices and LCDs, resistprocessing is performed for a substrate to be processed by a techniquecalled photolithography. This technique includes a series of steps ofapplying a resist solution to, for example, a semiconductor wafer(hereinafter, referred to as a wafer) to form a solution film on itsfront face, exposing the resist film to light using a photomask, andthereafter performing a developing treatment to obtain a desiredpattern.

There is one method for the above-described coating treatment of theresist solution, in which, for example, as shown in FIG. 30, a coatingsolution is applied in a manner of so-called drawing with one strokesuch that the coating solution (the resist solution) made by mixing aresist that is a component of a coating film and a solvent is dischargedonto a wafer front face from a nozzle 10 while the nozzle 10 providedabove the wafer W is being reciprocated in an X-direction and the waferW is intermittently moved in a Y-direction. Numeral 12 in FIG. 30denotes a mask which covers a region other than a circuit formationregion 11 of the wafer.

For carrying out the above-described method, it is considered to bepreferable that the wafer is carried into a reduced-pressure drying unitfor reduced-pressure drying immediately after the coating solution isapplied onto the wafer because a solvent having a low vaporization isused as the solvent contained in the coating solution and the uniformityof the film thickness of the coating film is secured by quickly removingthe solvent from the front face of the wafer.

FIG. 31 is a view showing a conventional reduced-pressure drying unit inwhich numeral 13 denotes a hermetic container constituted by a lid body14 and a mount 15, and a ceiling portion of the lid body 14 is formedwith an opening 14 a. The opening 14 a can communicate with a vacuumpump 16 through an exhaust pipe 14 b to reduce the pressure in thehermetic container 13. In such a unit, the wafer W is mounted on themount 15 and heated by a not shown heater, and the vacuum pump 16 isactuated to reduce the pressure in the hermetic container 13, therebycausing the solvent, for example, a thinner or the like remaining on thefront face of the wafer W to vaporize (dry) and the vaporized solvent tobe sucked toward the vacuum pump 16 side, so that the resist componentin the coating solution remains on the front face of the wafer W.

Meanwhile, a coating solution 17 on the front face of the wafer, whencarried into the reduced-pressure drying unit, is rounded, for example,as shown in FIG. 32, at a peripheral region of the wafer (a regioninside by a predetermined distance, for example, about 20 mm from theperiphery) due to a surface tension of the coasting solution itself.Therefore, it is considered to provide a current plate 18 above thewafer W mounted on the mount 15 in such a manner that the current plate18 faces the wafer W as shown by a dotted line in FIG. 31. When thecurrent plate 18 is provided as described above and the pressure in thehermetic container 13 is reduced, an air current is formed which spreadsoutward between the current plate 18 and the wafer W to cause thecoating solution to spread toward the periphery on the front face of thewafer.

Therefore, if the current plate 18 is provided and reduced-pressuredrying processing is performed, the coating solution is drawn toward theperiphery as shown in FIG. 33, resulting in an extremely large thicknessof the coating film at the peripheral region. The coating film with arounded shape or an accumulated portion at the peripheral region asdescribed above cannot be used as a circuit formation region because theperipheral region of the coating film is greatly different in filmthickness from the center region. Hence, there is a request that thecircuit formation region occupies an area as large as possible toimprove the yield of chips per wafer, and thus a significant problem isa control of the film thicknesses at the center region and theperipheral region in the coating film formed on the front face of thewafer.

SUMMARY OF THE INVENTION

The present invention is made due to such circumstances, and it is anobject of the present invention to provide a technique capable ofsecuring a high in-plane uniformity of film thickness by controlling thefilm thickness of a coating film during reduced-pressure drying in areduced-pressure drying unit for a substrate provided, for example, in acoating film forming apparatus.

In order to attain the above object, according to a first aspect of thepresent invention, a reduced-pressure drying unit of the presentinvention comprises: a hermetic container provided therein with a mountfor mounting thereon a substrate coated with a coating solution made bymixing a component of a coating film and a solvent; a vacuum exhausterconnected to the hermetic container through an exhaust passage forreducing a pressure in the hermetic container to vaporize the solventfrom the coating solution on the substrate; a current member provided toface a front face of the substrate mounted on the mount; and a currentmember raising and lowering mechanism for raising and lowering thecurrent member, wherein the current member is raised and lowered by thecurrent member raising and lowering mechanism to change in heightposition while the pressure inside the hermetic container is reduced tovaporize the solvent from the coating solution on the substrate.

According to another aspect, a reduced-pressure drying unit of thepresent invention comprises: a hermetic container provided therein witha mount for mounting thereon a substrate coated with a coating solutionmade by mixing a component of a coating film and a solvent; a heaterprovided in the mount for heating the substrate; a vacuum exhausterconnected to the hermetic container through an exhaust passage forreducing a pressure in the hermetic container to vaporize the solventfrom the coating solution on the substrate; and an annular member madeof a material having a heat conductivity different from that of themount, provided on the mount and coming into contact with a peripheralregion of a rear face of the substrate.

According to still another aspect, a reduced-pressure drying unit of thepresent invention comprises: a hermetic container provided therein witha mount for mounting thereon a substrate coated with a coating solutionmade by mixing a component of a coating film and a solvent; a vacuumexhauster connected to the hermetic container through an exhaust passagefor reducing a pressure in the hermetic container to vaporize thesolvent from the coating solution on the substrate; and a plurality ofaligning members provided at positions outside the mount and apart froma center position of the mount by equal distances in radial directions,wherein the plurality of aligning members synchronously move insubstantially horizontal directions from the positions outside thesubstrate to positions to come into contact with an edge of thesubstrate to align the center position of the mount and a centerposition of the substrate.

According to yet another aspect, a reduced-pressure drying unit of thepresent invention comprises: a hermetic container provided therein witha mount for mounting thereon a substrate coated with a coating solutionmade by mixing a component of a coating film and a solvent; a vacuumexhauster connected to the hermetic container through an exhaust passagefor reducing a pressure in the hermetic container to vaporize thesolvent from the coating solution on the substrate; a supporting memberprovided at the mount for supporting the substrate while slightlylifting the substrate from a front face of the mount; and a ventilationpassage formed in the mount and communicating with an outside of thehermetic container.

According to still another aspect, the present invention is a method forforming a coating film on a substrate which comprises: a step ofapplying to a front face of the substrate a coating solution made bymixing a component of a coating film and a solvent; a step of mountingthe substrate coated with the coating solution in a hermetic container;a reduced-pressure drying step of reducing a pressure in the hermeticcontainer by exhausting an air therein by a vacuum exhauster to vaporizethe solvent in the coating solution applied on the substrate; a firststep, performed in the reduced-pressure drying step, of positioning acurrent member so that the current member faces the substrate at a firstposition above the substrate mounted in the hermetic container; and asecond step, performed in the reduced-pressure drying step and after thefirst step, of moving the current member so that the current memberfaces the substrate at a second position different from the firstposition.

According to still another aspect, the present invention is a method forforming a coating film on a substrate which comprises: a step ofapplying to a front face of the substrate a coating solution made bymixing a component of a coating film and a solvent; a step of mountingthe substrate coated with the coating solution on a top face of a mountin a hermetic container; subsequently, a step of aligning centerpositions of the substrate and the mount by an aligning member; and areduced-pressure drying step of reducing a pressure in the hermeticcontainer by exhausting an air therein by a vacuum exhauster to vaporizethe solvent in the coating solution applied on the substrate.

According to the present invention, an exhaust current flowing outwardfrom the center is formed between the current member and the substrateduring the reduced-pressure drying processing, but the liquid flow ofthe coating solution on the substrate is controlled by changing theheight position of the current member in the reduced-pressure dryingprocessing, thereby controlling the film thickness of the coating filmon the front face of the substrate. This prevents a rounded shape or anaccumulated portion of the coating solution at a peripheral region ofthe substrate, so that the film thicknesses of the coating solution aremade uniform between the center region and the peripheral region,resulting in improved uniformity of film thickness.

Further, according to the present invention, the substrate is heated bythe heater provided in the mount, but the peripheral region of thesubstrate is in contact with the annular member which has a heatconductivity different from that of the mount, thereby causing differenttemperatures and accordingly different vaporization rates of the solventcontained in the coating solution between the center region and theperipheral region of the substrate. Consequently, it is possible tocontrol the film thickness of the coating film on the front face of thesubstrate, so that the film thicknesses of the coating solution are madeuniform between the center region and the peripheral region, resultingin improved uniformity of film thickness.

Further, according to the present invention, the substrate can bemounted on the mount with the center of the mount and the center of thesubstrate aligned with each other, so that uniform reduced-pressuredrying processing can be performed.

Furthermore, according to the present invention, when the hermeticcontainer is returned from the reduced-pressure atmosphere to theatmospheric pressure, the reduced-pressure state is quickly releasedalso on the rear face side of the substrate mounted on the mount becauseof air leakage from the ventilation passage, thereby preventing thecenter portion of the rear face side of the substrate from being suckedto the mount for prevention of warpage of the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plane view showing a whole structure, in an embodiment, of acoating film forming apparatus in which a reduced-pressure drying unitaccording to the present invention is installed;

FIG. 2 is a perspective view showing the whole structure in the aboveembodiment;

FIG. 3 is a schematic cross-sectional view showing a configuration of ashelf unit used in the above embodiment;

FIG. 4 is a vertical cross-sectional view for explaining a coating unitused in the above embodiment;

FIG. 5 is a plane view for explaining the coating unit in FIG. 4;

FIG. 6 is a vertical cross-sectional view showing a reduced-pressuredrying unit installed in the shelf unit in FIG. 3;

FIG. 7 is a characteristic diagram showing a curved line of a pressurein the reduced-pressure drying unit;

FIG. 8 is a side view for explaining another embodiment of thereduced-pressure drying unit according to the present invention;

FIG. 9 is a cross-sectional view for explaining still another embodimentof the reduced-pressure drying unit according to the present invention;

FIG. 10 is a characteristic diagram showing a curved line of a pressurein the reduced-pressure drying unit;

FIG. 11 is a cross-sectional view for explaining still anotherembodiment of the reduced-pressure drying unit according to the presentinvention;

FIG. 12 is a cross-sectional view for explaining still anotherembodiment of the reduced-pressure drying unit according to the presentinvention;

FIG. 13 is a plane view for explaining still another embodiment of thereduced-pressure drying unit according to the present invention;

FIG. 14 is a cross-sectional view for explaining still anotherembodiment of the reduced-pressure drying unit according to the presentinvention;

FIG. 15 is a cross-sectional view for explaining still anotherembodiment of the reduced-pressure drying unit according to the presentinvention;

FIG. 16 is a cross-sectional view for explaining still anotherembodiment of the reduced-pressure drying unit according to the presentinvention;

FIG. 17 is a side view for explaining still another embodiment of thereduced-pressure drying unit according to the present invention;

FIG. 18 is a perspective view showing a part of the still anotherembodiment;

FIG. 19 is a plane view for explaining a method for aligning a waferwith a mount;

FIG. 20 is a cross-sectional view for explaining the above method;

FIG. 21 is a cross-sectional view for explaining still anotherembodiment of the reduced-pressure drying unit according to the presentinvention;

FIG. 22 is a cross-sectional view for explaining still anotherembodiment of the reduced-pressure drying unit according to the presentinvention;

FIG. 23 is a cross-sectional view for explaining still anotherembodiment of the reduced-pressure drying unit according to the presentinvention;

FIG. 24 is a cross-sectional view for explaining still anotherembodiment of the reduced-pressure drying unit according to the presentinvention;

FIG. 25 is a cross-sectional view for explaining still anotherembodiment of the reduced-pressure drying unit according to the presentinvention;

FIG. 26 is a plane view for explaining still another embodiment;

FIG. 27 is a cross-sectional view for explaining still anotherembodiment of the reduced-pressure drying unit according to the presentinvention;

FIG. 28 is a cross-sectional view showing another example of thereduced-pressure drying unit;

FIG. 29 is a cross-sectional view showing an example of a configurationof the inside of another mount;

FIG. 30 is a perspective view for explaining a method of coating aresist solution;

FIG. 31 is a cross-sectional view for explaining a conventionalreduced-pressure drying unit;

FIG. 32 is a cross-sectional view showing a state of a coating filmafter the performance of reduced-pressure drying processing in theconventional reduced-pressure drying unit; and

FIG. 33 is a cross-sectional view showing another state of a coatingfilm after the performance of the reduced-pressure drying processing inthe conventional reduced-pressure drying unit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First of all, an entire configuration of a coating film formingapparatus in which a reduced-pressure drying unit according to thepresent invention is installed will be briefly explained below withreference to FIG. 1 to FIG. 3. In the drawings, numeral 21 denotes acassette station, in which a cassette mounting section 22 for mountingthereon cassettes C in which, for example, 25 wafers W are housed and adelivery arm 23 for delivering and receiving the wafers W to/from themounted cassette C are provided. A processing section S1 is connected tothe back side of the delivery arm 23. A main carrier 24 is provided inthe center part of the processing section S1 and, in such a manner tosurround the main carrier 24, a coating and developing system unit 25including a plurality of coating units 25A and developing units 25B isdisposed, for example, on the right-hand side as seen to the back sideand shelf units U1, U2, and U3 including heating and cooling systemunits and the like multi-tiered are disposed on the left-hand side, thefront side, and the back side respectively.

The shelf units U1, U2, and U3 are constituted by combining various typeof units for performing pre-process and post-process of the coatingunits 25A. This combination includes, for example, a reduced-pressuredrying unit 26 which dries, in a reduced pressure atmosphere, the waferW coated with a coating solution on the front face in the coating unit25A to vaporize a solvent contained in the coating solution, a heatingunit for heating (baking) the wafer W, a cooling unit for cooling thewafer W, a hydrophobic processing unit, and the like as typified by theshelf units U2 and U3, for example, shown in FIG. 3. It should be notedthat a delivery unit including a delivery table for delivering andreceiving the wafer W is also installed in each of the shelf units U2and U3. Further, the above-described main carrier 24 is configured, forexample, to be freely ascendable and descendable, movable forward andbackward, and rotatable about the vertical axis so as to be capable ofdelivering and receiving the wafer W to/from the coating units 25A, thedeveloping units 25B, and each unit constituting the shelf units U1, U2,and U3.

To the back side of such a processing section S1, an aligner S3 isconnected via an interface section S2. The interface section S2 deliversthe wafer W between the processing section S1 and the aligner S3 by acarrier arm 27 which is configured, for example, to be freely ascendableand descendable, movable leftward and rightward and forward andbackward, and rotatable about the vertical axis.

The flow of the wafer W in such a coating film forming apparatus isbriefly explained. First of all, when a cassette C is carried into thecassette station 21, a wafer W is taken out by the delivery arm 23.Then, the wafer W is delivered from the delivery arm 23 via the deliveryunit in the shelf unit U2 to the main carrier 24. The wafer W issubjected to hydrophobic processing in the hydrophobic processing unitand thereafter carried into the coating unit 25A, where the wafer W iscoated with a resist solution that is the coating solution.

Subsequently, the wafer W coated with the coating solution is carried bythe main carrier 24 to the reduced-pressure drying unit 26, where thesolvent contained in the coating solution on the front face of the waferW is vaporized to dry by a predetermined method. The wafer W after theprocessing passes through steps in a reverse order to that when carriedinto the reduced-pressure drying unit 26, is carried out by the maincarrier 24, and is carried to the cooling unit in which the next step isperformed. Thereafter, the wafer W is carried via the interface sectionS2 and the carrier arm 27 to the aligner S3, where the wafer W isexposed to light via a mask corresponding to a pattern. The wafer afterthe exposure is carried to the processing section S1 through a reverseroute, and carried via the cooling unit to the developing unit 25B andsubjected to a developing treatment to be formed with a resist mask.Thereafter, the wafer W is returned to the original cassette C through areverse route.

Next, explanation is made on the coating unit 25A with reference to FIG.4 and FIG. 5. Although a casing which forms an outer body of the coatingunit 25A is omitted here, for example, a hollow case body 30, whose sideis formed with an opening (not shown) for carrying in/out the wafer Wtherethrough, is provided in the not shown casing. Inside the case body30, a substrate holder 31 which horizontally holds the wafer W byvacuum-sucking the rear face of the wafer W and a raising and loweringmechanism 32 which supports the lower side of the substrate holder 31and raises and lowers the substrate holder 31, are provided. The ceilingportion of the case body 30 is formed with a slit 33 extending in anX-direction, so that a nozzle 34 for supplying the resist solution thatis the coating solution can be moved in the X-direction above the slit33 by a driver 35 with a discharge hole 34 a at the lower tip projectinginto the case body 30 through the slit 33.

On the other hand, the substrate holder 31 and the raising and loweringmechanism 32 are integrated with a supporter 36 in a flat plate shapewhich is provided under the wafer held by the substrate holder 31 toface the rear face of the wafer. On the bottom face of the supporter 36,for example, two rails 37 a extending in a Y-direction are disposed, anda ball screw 37 b is provided in parallel to the rails 37 a in thevicinity of the bottom face, so that a motor 38 rotates the ball screw37 b to cause the supporter 36 to move in the Y-direction guided by therails 37 a.

In the coating unit 25A, the wafer W carried into the coating unit 25Aby the main carrier 24 is substantially horizontally held with the rearface thereof sucked by the substrate holder 31. Then, after the nozzle34 is positioned above the wafer W, the nozzle 34 is moved in theX-direction while discharging the coating solution as well as the waferW is intermittently moved in the Y-direction by the supporter 36, sothat the coating solution is applied in a manner of a so-called drawingwith one stroke.

Next, explanation is made on one embodiment of the reduced-pressuredrying unit 26 realizing the reduced-pressure drying unit according tothe present invention. In FIG. 6, numeral 41 denotes a mount constitutedby a temperature regulating plate in which, for example, a Peltierelement is embedded, an aluminum material, or the like The wafer W isheld to be slightly lifted from the front face of the mount 41 bysupport pins 41 a which slightly project from the mount. Above the mount41, a lid body 42 is provided which is constituted by, for example, analuminum material. The lid body 42 is made freely ascendable anddescendable by the function of a raising and lowering mechanism 43 whichis composed of a holding arm 43 a, a driver 43 b, and the like. The lidbody 42, when lowered, comes into hermetically contact with theperipheral portion of the mount 41 through an O-ring 40 that is asealing material to constitute a hermetic container 4 that makes theatmosphere in which the wafer W is located into a hermetic atmosphere.

In the vicinity of the front face of the mount 41, a heater H isembedded (see FIG. 6) for heating the wafer W in reduced-pressuredrying, which is constituted by, for example, a resistance heatingelement or the like. Inside the mount 41, three lift pins 44 areprovided therethrough to deliver and receive the wafer W to/from themain carrier 24, and raised and lowered by a first raising and loweringdevice 44 b such as, for example, an air cylinder through a firstraising and lowering plate 44 a.

In order to suck the atmosphere in the hermetic container 4, a ceilingportion 42 a of the lid body 42 is formed with an opening 45 a to whichone end of an exhaust pipe 45 forming an exhaust passage is connectedwhich is made of, for example, stainless steel. The exhaust pipe 45 runsthrough a not shown casing of the reduced-pressure drying unit 26 and anot shown casing of the processing section S1 and via an opening andclosing valve V1, and the other end thereof is connected to a vacuumpump 46 that is a vacuum exhauster provided, for example, in a cleanroom.

In a space facing the wafer W in the lid body 42, a current plate 5 thatis a plate-like current member is provided in such a manner to face thewafer W mounted on the mount 41 and have a gap with respect to any ofthe ceiling portion 42 a and side walls 42 b of the lid body 42. Thecurrent plate 5 is connected with a plurality of, for example, threesubstantially vertical support rods 51 that are provided through themount 41 and connecting members 52, for example, outside the wafer W.The support rods 51 can be raised and lowered by a current plate raisingand lowering mechanism 53 constituting a current member raising andlowering mechanism composed of a second raising and lowering plate 53 aand a second raising and lowering device 53 b such as, for example, anair cylinder, so that the current plate 5 is configured to be ascendableand descendable above the wafer W so as to change in height positionwith respect to the wafer W.

In order to prevent the atmosphere in which the wafer W is located fromcommunicating with the external air via through holes 47 a for the liftpins 44 and through holes 54 a for the support rods 51 in this event,bellows 47 b and 54 b are provided between the peripheral portions ofthe first and second raising and lowering plates 44 a and 53 a and themount 41 respectively. By providing the current plate 5 in the hermeticcontainer 4 as described above, a uniform exhaust current is formedalong inner walls of the lid body 42 in reduced-pressure drying.

The hermetic container 4 is provided with a pressure sensor 55constituting a pressure detecting section for detecting the pressure inthe container 4, for example, on the inner wall of the lid body 42, sothat the height position of the current plate 5 can be changed by acontroller 56 through the current plate raising and lowering mechanism53 based on the detection value by the pressure sensor 55.

Next, a reduced-pressure drying method performed in such areduced-pressure drying unit 26 is explained. First of all, the wafer Wwhich has been coated with the resist solution that is the coatingsolution in the preceding step is carried to the reduced-pressure dryingunit 26 by the main carrier 24. The carriage of the wafer W into thereduced-pressure drying unit 26 is performed in such a manner that a notshown arm of the main carrier 24 first approaches to a position abovethe mount 41 with the lid body 42 and the current plate 5 raised, thenthe lift pins 44 are raised to receive the wafer W from the arm, andthereafter the lift pins 44 are lowered.

Thereafter, the current plate 5 is lowered to an initial position, forexample, a position where the distance between the front face of thewafer W and the rear face of the current plate 5 is 5 mm, and then thelid body 42 is lowered to form the hermetic container 4. Subsequently,the current plate 5 is once lowered to a position where the aforesaiddistance is, for example, 3 mm, and then the opening and closing valveV1 is opened to start reducing the pressure by the vacuum pump 46. Then,the current plate 5 is lowered to a first position where the distancebetween the front face of the wafer W and the rear face of the currentplate 5 is, for example, 1 mm to make a first distance (gap) between thefront face of the wafer and the rear face of the current plate, and thepressure is reduced for a predetermined period.

The coating solution (the resist solution) applied to the front face ofthe wafer W is made by mixing the component of the resist film that isthe coating film, the solvent, for example, a thinner or the like, andwater. When the inside of the hermetic container 4 is made into thereduced-pressure atmosphere, the air in the container 4 and the solventand water in the coating solution vaporize and are sucked to the exhaustpipe 45 side via the opening 45 a. Since the exhaust current in thehermetic container 4 is formed to detour the current plate 5 in thisevent, solvent vapor vaporizing from the wafer W hits against thecurrent plate 5 to change in direction outward and uniformly spreads ina radial direction together with the exhaust current toward the opening45 a.

As described above, an air current flowing outward from the center ofthe wafer W is generated between the wafer W and the current plate 5,and this flow of the air current becomes stronger the smaller the gapbetween the current plate 5 and the wafer W is, and the flow becomesweaker the larger the gap is. Accordingly, when the pressure reductionis performed in the state where the gap between the current plate 5 andthe wafer W is made as small as 1 mm, the coating solution spreads bythe strong air current spreading outward between the current plate 5 andthe wafer W, so that the coating solution sufficiently spreads out tothe peripheral region of the wafer W In order to restrain a roundedshape of the coating solution at the peripheral region of the wafer W,when the coating solution is spread out to the peripheral region of thewafer W as described above, the current plate 5 is raised at apredetermined timing from the first position to a second position thatis higher than the first position, for example, a position where thedistance between the front face of the wafer W and the rear face of thecurrent plate 5 is 5 mm to make a second distance (gap) that is largerthan the first distance between the front face of the wafer and the rearface of the current plate, and the reduced-pressure drying is continuedfor a predetermined period.

In this arrangement, the gap between the current plate 5 and the wafer Wincreases to weaken the air current flowing outward, which restrainsliquid flow of the coating solution. This prevents the coating solutionfrom increasing in thickness at the peripheral region of the wafer,resulting in improved in-plane uniformity of the thickness of thecoating film. The reduced-pressure drying is performed as describedabove to vaporize the solvent and water from the coating solution on thefront face of the wafer so as to dry the coating film. Thereafter, theinside of the container 4 is returned to a normal pressure by leakingthe air therein, the lid body 42 and the current plate 5 are raisedbefore the lift pins 44 are raised, and then the wafer W is delivered tothe main carrier 24.

As described above, this embodiment is characterized in that the heightposition of the current plate 5 is changed to thereby change themagnitude of the gap between the current plate 5 and the wafer W inreduced-pressure drying processing, thereby controlling the liquid flowof the coating solution on the wafer W so as to improve the uniformityof the film thickness of the coating film. The timing of changing theheight position of the current plate 5 in such an arrangement isdetermined based on the pressure in the hermetic container 4, and theheight position of the current plate 5 is changed via the controller 56.

In other words, when the hermetic container 4 is reduced in pressure,the pressure in the hermetic container 4 changes as a pressure curvedline shown in FIG. 7. More specifically, the air in the hermeticcontainer 4 is kept exhausted from time t0 to time t1, during which thepressure inside the hermetic container 4 is sharply reduced frompressure P0 to pressure P1. Subsequently, time t1 is a point of timewhen the thinner that is the solvent starts vaporizing from the coatingsolution on the front face of the wafer, and the thinner keepsvaporizing from time t1 to time t3, during which the pressure inside thecontainer 4 is gradually reduced from pressure P1 to pressure P3. Then,time t3 is a point of time when the water contained in the coatingsolution on the front face of the wafer starts vaporizing, and thethinner remaining in the coating solution and the water keep vaporizingfrom time t3 to time t4, during which the pressure inside the hermeticcontainer 4 is again sharply reduced from pressure P3 to pressure P4.

In the case of the inside of the hermetic container 4 kept at a constanttemperature, the thinner is vaporizing (evaporating) even in the statewhere the pressure inside the hermetic container 4 is not reduced, andwhen the pressure inside the hermetic container 4 is sharply reduced,the thinner immediately reaches its boiling point to a state ofvaporizing from below the surface of the thinner. However, if thethinner is allowed to vaporize from below the surface thereof asdescribed above, the coating film becomes rough. Therefore, thedisplacement by the vacuum pump 46 is determined so that the decrease inpressure in the container 4 becomes a bit less sharp in theabove-described embodiment. When the pumping speed by the vacuum pump 46is set a bit low, the thinner vigorously vaporizes a short while beforethe boiling point. In accordance with the balance between existence ofthe gas which vaporized at that time and the pumping speed, the pressurein the container 4 gradually inclines downward such as when ranging frompressure P1 to pressure P3. In the present invention, “the state of thethinner vigorously vaporizing” is called “vaporization of the thinner”,and this state shall include states of the thinner at the boiling pointand before the boiling point.

As for the state of the coating solution on the front face of the wafer,the fluidity of the coating solution is influenced by the vaporizationof the thinner that is the solvent and further the fluidity is great atthe beginning of the vaporization because of a large amount of solvent,and thus it is necessary to change the height position of the currentplate 5 in the vaporization of the solvent. Specifically, the currentplate 5 may be located at any height position from time t0 to time t1during which the air in the container 4 is exhausted and from time t3 totime t4 during which the water vaporizes from the coating solution onthe front face of the wafer, and it is required to control the heightposition of the current plate 5 from time t1 to time t3 during which thethinner that is the solvent is vaporizing from the coating solution.

During the vaporization of the solvent, it is necessary to increase thefluidity of the coating solution to thereby sufficiently spread out thecoating solution to the peripheral region of the wafer in the earlyperiod, and thereafter it is necessary to restrain the fluidity of thecoating solution to prevent the coating solution at the peripheralregion of the wafer from becoming too high. The fluidity of the coatingsolution here changes in accordance with the magnitude of the aircurrent generated between the wafer W and the current plate 5 such thatthe air current becomes stronger the smaller the gap between the wafer Wand the current plate 5 is, and the air current becomes weaker thelarger the gap is, as already described.

In this event, the pressure in the container 4 is gradually reduced frompressure P1 to pressure P3 in a period from time t1 to time t3 asdescribed above, and thus at the time (time t2) when the pressurereaches a set pressure P2 which is previously obtained, the currentplate 5 is raised from the first position to the second position.Further, the height of the current plate 5 may be set at any heightbefore time t1 and after time t3 because it does not influence thecoating film. In this example, the height of the current plate 5 is setat the first position from time t1 to time t2 and is set at the secondposition from time t2 to time t4 in order to eliminate an effort to movethe current plate 5. The set pressure P2, the first height position (thefirst gap), and the second height position (the second gap) areappropriately selected here in accordance with the size of the wafer,processing conditions such as the temperature and the pressure insidethe hermetic container 4, the component of the coating solution, and thelike.

According to the above-described embodiment, the height position of thecurrent plate 5 is changed to thereby change the magnitude of the gapbetween the current plate 5 and the wafer W in reduced-pressure dryingprocessing, thereby controlling the liquid flow of the coating solution.Therefore, it is possible to control the film thickness of the coatingfilm on the front face of the wafer, thereby restraining a rounded shapeand an accumulated portion of the coating solution at the peripheralregion of the wafer to uniform the film thicknesses at the center partand the peripheral region of the coating film, resulting in improveduniformity of the thickness. This makes it possible to fabricate chipseven in the vicinity of the outer periphery of the wafer to improve theyield of chips per wafer. Further, the improved uniformity of the filmthickness of the coating film stables the film thickness to enablestable fabrication of devices, resulting in improved throughput.

Further, the height of the current plate 5 is controlled based on thepressure in the hermetic container 4 to bring about a high reliabilityin the timing of changing the height position of the current plate 5, sothat processing can be performed stably at all times to provide a highuniformity of the film thickness of the coating film, resulting in highthroughput.

In this embodiment, the wafer W is mounted on the mount 41 and the lidbody 42 is lowered to form the hermetic container 4, and thereafter thecurrent plate 5 is first lowered to the first position, the opening andclosing valve V1 is opened, and the vacuum pump 46 starts reduction ofpressure and keeps the reduction for a predetermined period. Then, whenthe pressure in the container 4 reaches the pressure P2, the currentplate 5 may be raised from the first position to the second position andreduced-pressure drying may be continued for a predetermined period.

Next, other embodiments of the reduced-pressure drying unit 26 will beindividually explained, and the same members are assigned the samenumerals in the drawings hereafter. The below examples may be combinedwith the already-described reduced-pressure drying unit 26, or otherembodiments may be combined with each other.

In the example in FIG. 8, instead of controlling the height of thecurrent plate 5 based on the pressure in the hermetic container 4, thefilm thickness of a coating solution A on the front face of the wafer Wis measured by a film thickness sensor 57 which utilizes, for example, aCCD or light to control the height of the current plate 5 based on themeasurement. In this case, the control is conducted such that, forexample, the film thickness at the center part and the film thickness atthe peripheral part of the coating solution on the front face of thewafer W are measured and the difference between the film thicknesses iscalculated to raise the current plate 5 in height from the firstposition to the second position when a value of the above differencebecomes a predetermined value or lower. In this case, a high uniformityof the film thickness of the coating film can also be secured so that ahigh throughput can be obtained.

Meanwhile, the vaporization period of the solvent may be controlled asin the following manner. In the example shown in FIG. 9, a pressureadjuster 58, which is constituted, for example, by a pressure adjustingvalve, is provided between the exhaust pipe 45 and the vacuum pump 46.The pressure in the hermetic container 4 is detected by the pressuresensor 55, and the pressure adjuster 58 is controlled by the controller56 based on the detection value to control the displacement (pumpingspeed) in the hermetic container 4, thereby adjusting the vaporizationperiod of the solvent in the coating solution. When, for example, apressure adjusting valve is used as the pressure adjuster 58, thedisplacement can be controlled by adjusting the opening of the valve. Inthis case, as shown in FIG. 10, while a change in the displacement doesnot change the gradient of the pressure curved line from time t1 to timet3, an increase or decrease in the pumping speed during a period fromtime t1 to time t3 makes it possible to adjust the vaporization periodof the solvent. More specifically, an increase in the displacementreduces the vaporization period of the solvent as shown by a one-dottedchain line in FIG. 10, and a decrease in the displacement increases thevaporization period of the solvent as shown by a dotted line in FIG. 10.

In the case of, for example, a coating solution using a thinner, whichquickly vaporizes, as its solvent being applied on the front face of thewafer, it might be difficult to precisely control the spreading state ofthe coating solution by controlling the height position of the currentplate 5 because the spreading rate of the coating solution is high.However, the vaporization period of the solvent in the coating solutionis increased as in this example results in a decrease in the spreadingrate of the coating solution. Therefore, it is possible to sufficientlycontrol the spreading state of the coating solution, even if it is thecoating solution using a thinner, which quickly vaporizes, as itssolvent, by controlling the height position of the current plate 5, sothat the control of the film thickness of the coating solution caneasily be conducted.

The example shown in FIG. 11 has a configuration in which, inside thehermetic container 4, a heater is provided for heating the wafer W at apoint of time t3 on the curved line of the pressure inside the hermeticcontainer 4 shown in FIG. 7. The heater may be provided at any placeinside the hermetic container 4 such as in the mount 41 or in the lidbody 42, and a heater 59 composed of, for example, a resistance heatingelement is provided, for example, inside the current plate 5 in thisexample.

As described above, the heating of the wafer W at the point of time t3on the curved line of the pressure inside the hermetic container 4 shownin FIG. 7 increases the vaporization rates of the thinner remaining inthe coating solution on the front face of the wafer and water containedin the coating solution due to the heating. Therefore, the thinnerquickly vaporizes by the heating even when, for example, a coatingsolution using a thinner, which slowly vaporizes, as its solvent isapplied to the front face of the wafer and when a long period isrequired for vaporization of all the thinner. Accordingly, the periodrequired for the reduced-pressure drying processing is reduced ascompared to the case without heating. The reason why the heating isstarted at the point of time t3 is that the film thickness can be moreprecisely controlled at a lower vaporization rate of the solvent in thestep of controlling the film thickness of the coating solution from timet1 to time t3.

In this case, the reduction in the pressure inside the hermeticcontainer 4 may be stopped or not during the heating by the heater 59.The timing of turning on the heater 59 may be determined based on thedetection value of the pressure inside the hermetic container 4 or basedon the detection value of the film thickness of the coating solution.Further it is also adoptable to perform the heating of the wafer W andthe adjustment of the displacement in the hermetic container 4 as shownin FIG. 9 in combination, to precisely control the film thickness byincreasing the period from time t1 to time t3, and to adjust the totalprocessing period required for the reduced-pressure drying step byreducing the period after time t3.

In order to spread the coating solution uniformly in the wafer plane inthe above configuration, it is important to arrange the current plate 5in parallel to the wafer W, and thus an example of a mechanism providedto make the current plate 5 parallel to the wafer W is explained nextwith reference to FIG. 12 to FIG. 15.

In FIG. 12, numeral 60 denotes a hang-supporter for hang-holding thecurrent plate 5 on the lid body 42, and supporters 60 are connected tothe current plate 5 at plural, for example, three points as shown inFIG. 13 so that the current plate 5 is hang-supported by, for example,three supporters 60. Each of the supporter 60 comprises, as shown inFIG. 14, a substantially vertical holding rod 61, a collar portion 62provided at the top end of the holding rod 61, and a spring portion 63wound around the holding rod 61, in which the bottom end of the holdingrod 61 is joined to the front face of the current plate 5 facing the lidbody 42 with a spherical joint portion 64.

In the ceiling portion 42 a of the lid body 42 facing the current plate5, a recessed portion 42 b having a size enough for the collar portion62 to move therein is formed at a position facing the holding rod 61,and an opening 42 c of the recessed portion 42 b is made narrow so thatthe holding rod 61 can pass therethrough but the collar portion 62cannot. Thereby, when the current plate 5 is raised and lowered by alater-described current plate raising and lowering mechanism, theholding rod 61 is ascendable and descendable by the height of therecessed portion 42 d while hang-supporting the current plate 5.

Next, a current plate raising and lowering mechanism 65 constituting acurrent member raising and lowering mechanism is explained. The currentplate 5 comprises, as shown in FIG. 12 and FIG. 15, a plurality of, forexample, three leg parts 50 at positions on the rear face side thereofand outside the wafer W mounted on the mount 41. The leg part 50 isformed to extend substantially vertically into the inside of the frontface of the mount 41 located thereunder, and the bottom end thereof isconnected to a later-described raising and lowering rod.

The current plate raising and lowering mechanism 65 comprises, as shownin FIG. 12 and FIG. 15, a plurality of, for example, three raising andlowering rods 66 for pressing the rear face of the current plate 5through the leg parts 50, a raising and lowering plate 67 connected tothe bottom end of all of the raising and lowering rods 66, and a raisingand lowering device 68 for raising and lowering the raising and loweringplate 67. The raising and lowering rods 66 are provided such as to beraised and lowered at positions corresponding to the leg parts 50 of thecurrent plate 5. Further, the leg parts 50 of the current plate 5, theraising and lowering rods 66, and the raising and lowering plate 67 areconfigured so that when the raising and lowering plate 67 raises andlowers the raising and lowering rods 66, the current plate 5 raised andlowered by the raising and lowering rods 66 can be kept highly parallelto the wafer W mounted on the mount 41.

A ventilation hole 66 a having a bore diameter, for example, 2 φ runsthrough the inside of the raising and lowering rod 66, and a region inthe vicinity of the top end of the raising and lowering rod 66 is formedto have a size enough for the bottom end of the leg part 50 of thecurrent plate 5 to be inserted. The other end side of the raising andlowering rod 66 which is not in contact with the current plate 5 isconnected to a first exhauster 66 b through an opening and closing valveV2. Numeral 66 c denotes a though hole of the raising and lowering rod66, and an O-ring 66 d constituting a sealing member is provided betweenthe though hole 66 c and the raising and lowering rod 66. Between themount 41 around the raising and lowering rod 66 and the raising andlowering plate 67, a bellows 66 e is provided for preventing the insideof the hermetic container 4 from communicating with the external airthrough the though hole 66 c.

The raising and lowering device 68 comprises, as shown in FIG. 12, asubstantially vertical ball screw 68 a, a supporter 68 b connected toone end of the raising and lowering plate 67, and a motor M1 forrotating the ball screw 68 a. The motor Ml rotates the ball screw 68 ato cause the supporter 68 b to ascend and descend along the ball screw68 a, whereby the current plate 5 is raised and lowered through theraising and lowering plate 67 and the raising and lowering rods 66 to beat a precise height. As a result, the current plate 5 raised and loweredby the raising and lowering rods 66 is raised and lowered while kepthighly parallel to the wafer W mounted on the mount 41.

Further, the hermetic container 4 in this example is provided withO-rings 69 a and 69 b constituting two sealing members having differentinner diameters at a connecting part between the mount 41 and the lidbody 42, and a groove portion 41 b is formed, as shown in FIG. 14,between the O-rings 69 a and 69 b, and the groove portion 41 b isconnected to a second exhauster 69 c through an opening and closingvalve V3.

In such a configuration, the current plate 5 is hang-supported by thehang-supporter 60 on the lid body 42 while kept in contact with theraising and lowering mechanism 65 through the leg parts 50, so that thecurrent plate 5 is raised and lowered with the ascent and descent of thelid body 42. For changing the height position of the current plate 5 inthe reduced-pressure drying processing, the raising and lowering rods 66of the current plate raising and lowering mechanism 65 push the rearface of the current plate 5 through the leg parts 50. In this event, forexample, in the above-described example, the current plate 5 is changedin height, in the reduced-pressure drying processing, between the firstposition 1 mm above the front face of the wafer W and the secondposition 5 mm above the front face. When the current plate 5 is firstlocated at the first position, the tips of the raising and lowering rods66 are made contact with the leg parts 50 of the current plate 5 and theinside of the raising and lowering rods 66 are sucked by the firstexhauster 66 b by opening the opening and closing valve V2.

This brings the current plate 5 into contact with the raising andlowering rods 66 inside the mount 41, so that particles generated in thevicinity of the connecting parts between the leg parts 50 of the currentplate 5 and the raising and lowering rods 66 in the time of raising andlowering influence a little the processing in the container 4. Further,the particles generated in the vicinity of the connecting parts betweenthem are discharged through the raising and lowering rods 66 by thesuction of the connecting parts between them, so that contamination withthe particles can be prevented further. The current plate 5 and theraising and lowering rods 66 may be configured to directly contact witheach other in this event, but the quantity of generated particlesincreases because they are in contact with each other at a positionhigher than the mount 41 in this case.

Since the parallelism of the current plate 5 is determined by the threeraising and lowering rods 66 and the current plate 5 itself ishang-supported on the lid body 42, a subtle gradient might occur in thecurrent plate 5 when raised and lowered. However, since the currentplate 5 and the holding rods 61 are connected to each other with thespherical joint portions 64, the gradient of the current plate 5 isabsorbed by the spherical joint portions 64, so that the current plate 5raised and lowered by the raising and lowering rods 66 are raised andlowered while keeping a high parallelism to the wafer W mounted on themount 41. This makes it possible to uniformly spread the coatingsolution on the front face of the wafer W so as to secure a higheruniformity of the film thickness.

Further, in this example, double O-rings 69 a and 69 b are provided andthe reduced-pressure drying processing is performed while the airtherebetween sucked by the second exhauster 69 c by opening the openingand closing valve V3. This permits the mount 41 and the lid body 42 toattach by the suction to each other more firmly, thereby preventing theexternal air from entering the container 4 through the space between themount 41 and the lid body 42 when the air inside the hermetic container4 is exhausted by the vacuum pump 46.

In the reduced-pressure drying unit 26 of the present invention, thecurrent plate raising and lowering mechanism constituting the currentmember raising and lowering mechanism may be configured as shown in FIG.16. Numeral 71 in FIG. 16 denotes a substantially horizontal ball screwand numeral 72 denotes a supporter, in which a motor M2 rotates the ballscrew 71 to cause the supporter 72 to move horizontally along the ballscrew 71.

On the other hand, a joint-connected part 73 is provided on the rearface side of the second raising and lowering plate which is denoted bynumeral 53 a in FIG. 16, and the joint-connected part 73 and thesupporter 72 are connected to respective ends of a joint 74 in the shapeof an elongated plate with rotation shafts 75 a and 75 b respectively.Thereby, when the supporter 72 is located at a position apart from thejoint-connected part 73, the joint 74 is placed such that thelongitudinal direction thereof is substantially horizontal, so that thecurrent plate 5 is disposed at a position close to the wafer W. Thesupporter 72 is moved to a position close to the joint-connected part 73by rotating the ball screw 71, whereby the longitudinal direction of thejoint 74 gradually becomes closer to vertical so that the current plate5 is raised to be apart from the wafer W (to be located at a higherposition). As described above, in this example, the height position ofthe current plate 5 is appropriately determined by adjusting thelongitudinal length of the joint 74 and the angle formed between thelongitudinal direction of the joint 74 and the wafer W.

In such a configuration, a mechanism that the supporter 72 is accuratelymoved in the horizontal direction by the ball screw 71 and a mechanismthat the supporter 72 and the second raising and lowering plate 53 a areconnected with the joint 74 are combined to change the height positionof the current plate 5 through the joint 74 by moving the supporter 72.Accordingly, the height of the current plate 5 can slowly be changed bydecreasing the rotation speed of the ball screw 71 at the beginning ofchanging the height of the current plate 5. This can prevent airturbulence when the solvent contained in the coating solution on thefront face of the wafer W, resulting in higher uniformity of the filmthickness of the coating film.

Next, still another embodiment of the reduced-pressure drying unit 26 ofthe present invention is explained with FIG. 17 and FIG. 18. Thisembodiment provides a thermal change to the peripheral region of thewafer W by providing a member in contact with the peripheral region ofthe rear face of the wafer W, on the mount 41 including the heater Htherein. Specifically, a ring member 8, which forms an annular memberhaving a cross section, for example, in the shape of the letter L, isprovided on the mount 41 constituting the hermetic container 4, so thatthe top face of the ring member 8 supports the peripheral part of therear face of the wafer W. The ring member 8 is made of, for example,aluminum, stainless steel, ceramics, or the like which is different inheat conductivity from the mount 41.

In such a configuration, heat conduction from the mount 41 changes inaccordance with the material of the ring member 8 and a gap 81 formedbetween the ring member 8 and the rear face of the wafer W. Therefore,the temperature of the wafer W varies between the center region and aregion in the vicinity of a portion in contact with the ring member 8(the peripheral region of the wafer), whereby the vaporization rate ofthe solvent varies between the center region and the peripheral regionof the wafer. More specifically, as the temperature of the wafer Wrises, the vaporization rate of the solvent in the region increases, andas the temperature drops, the vaporization rate of the solvent in theregion decreases. Accordingly, by conducting a control such that thetemperature of the wafer varies in plane by the difference in heatconductivity, the vaporization rate of the solvent differs in plane, sothat the film thickness can be controlled in the wafer plane asdescribed above.

In this example, the vaporization of the solvent in the coating solutionis controlled by the combination of the change in the height position ofthe current plate 5 and the variation in the temperature in wafer planeas already described, thereby making it possible to conduct a control sothat the film thickness of the coating film becomes uniform includingthe portion in the vicinity of the outer periphery of the wafer.Therefore, even if an outer peripheral region, outside the circuitformation region of the wafer, which is to be discharged is within asfew as 5 mm from the outer periphery, the coating film can be formedhaving a sufficiently uniform film thickness also in the region in thevicinity of the outer periphery.

In this case, the ring member 8 may be of a type such that the entiretop face of the ring member is in contact with the rear face of theperipheral region of the wafer W other than one having a cross sectionin the shape of the letter L. In this application, the temperature ofthe wafer is adjusted within the plane by the heat conductivity in thevicinity of a portion of the ring member 8 in contact with the wafer W,in which the shape and the material of the ring member 8 and theposition and the size of the contact portion thereof with the wafer areappropriately selected in accordance with the type of the coating filmto be formed and other processing conditions.

Further, in this embodiment, the ring member 8 is provided to vary theheat conduction in the center region and at the peripheral region of thewafer W, thereby adjusting the temperature of the wafer W in the planeso as to control the film thickness of the coating film. Therefore, thisembodiment may be configured such that the above-described current plateis not provided, and configured such that the current plate is providedbut its height position is not changed.

In the above embodiment, the wafer is delivered to the ring member 8,and, in this case, center positions of the ring member 8 and the wafereasily deviate from each other when the wafer is mounted on the ringmember 8. Since the deviation of the center position of the wafer asdescribed above decrease the uniformity of the film thickness of thecoating film, it is important to deliver the wafer onto the ring member8 with the center positions of the ring member 8 and the wafer Waligned. Next, a method of aligning the center positions of the ringmember 8 and the wafer W is explained.

In this method, the wafer W is first delivered onto the ring member 8,and thereafter, for example, as shown in FIG. 19, a plurality of, forexample, three aligning members 82 which are provided outside the waferW and apart from the center position of the ring member 8 by equaldistances are synchronously moved from waiting positions outside thewafer to alignment positions in contact with the outer edge of the waferW respectively to push the wafer W into alignment.

Each of the alignment members 82 comprises a plate-like body 82 a sothat a part of a side edge of the plate-like body 82 a pushes a part ofthe outer edge of the wafer W. Further one end of the plate-like body 82a is connected to a substantially vertical rotation shaft 83 b, a pulley83 a is connected to the other end of the rotation shaft 83 b, and abelt is stretched between the pulleys 83 a of the rotation shafts 83 b.Thereby, any rotation shaft 83 b is rotated by a not shown motor tocause all the rotation shafts 83 b to rotate synchronously.

The plate-like bodies 82 a of the aligning members 82 are synchronouslyrotation driven from the waiting positions to the alignment positions inthe above manner. The three aligning members 82 are configured to bemoved to the alignment positions to come into contact with the outeredge of the wafer as described above, so that the wafer W is pushed intoa position where the center position of the ring member 8 and the centerposition of the wafer W correspond with each other into alignment.Numeral 83 c in FIG. 20 denotes a bearing.

The alignment of the wafer by moving the aligning members 82 aftermounting the wafer W on the ring member 8 as described above permits thecenter positions of the wafer and the ring member 8 to correspond witheach other at all times, thereby stably improving the uniformity of thefilm thickness of the coating film to provide an improved throughput.

This embodiment is applicable to, other than the case of delivering thewafer onto the ring member 8, a case of delivering the wafer onto themount 41 and a case of delivering the wafer onto the support pins 41 aof the mount 41. In any case, the wafer is mounted on the ring member 8or the mount 41 while the center positions thereof aligned, so that thereduced-pressure drying processing with high uniformity can beperformed. Further, this embodiment is also applicable to a reducedpressure drying unit having a configuration without provision of thecurrent plate and the ring member. Further, a member on which the waferis mounted belongs to “the mount” of the present invention. Therefore,the ring member and the like shall be included in the mount.

FIG. 21 shows still another example of the reduced-pressure drying unit26 of the present invention and this example is characterized by themount on which the wafer W is mounted. In the mount 41 of this example,for example, a first ventilation passage 84 a is formed to run throughthe mount 41 in the vertical direction, for example, immediately outsidea region where the ring member 8 is provided, and a second ventilationpassage 84 b communicating with the through hole 47 a of the lift pin 44is formed starting from the first ventilation passage 84 a. In the firstventilation passage 84 a, an O-ring 84 c is provided at a positioncloser to the external air than a position where the second ventilationpassage 84 b branches off therefrom in order to prevent the external airfrom entering the hermetic container 4 through the ventilation passages84 a and 84 b.

In the case of no ventilation passages 84 a and 84 b being formed in themount 41 here, a reduction in the pressure in the hermetic container 4might cause the rear face of the wafer W to be sucked to the top face ofthe ring member 8 so that even if the inside of the container 4 isreturned from the reduced pressure atmosphere to the atmosphericpressure, the center region of the rear face of the wafer W is sucked tothe mount 41 because the rear face of the wafer W is still under thereduced pressure condition, resulting in a warped wafer. In theconfiguration where the mount 41 is provided with the ventilationpassages 84 a and 84 b as described above, however, air easily leaks tothe rear face side of the wafer W when the inside of the hermeticcontainer 4 is returned from the reduced pressure atmosphere to thenormal pressure atmosphere to provide the atmospheric pressure to therear face side of the wafer W, so that suction between the center regionof the rear face of the wafer W and the mount 41 is restrained toprevent warpage of the wafer.

This configuration is applicable to a reduced-pressure drying unithaving a configuration without provision of the current plate and thering member. This configuration can be applied because even the mount 41having a configuration without provision of the ring-member 8 asdescribed above mounts the wafer W on the support pins 41 a to form aspace between the center region of the wafer W and the mount 41.Therefore, the ring member and the support pin shall be included in thesupporting member of the present invention.

FIG. 22 is still another example of the reduced-pressure drying unit 26of the present invention in which the current plate 5 is provided to beparallel to the wafer W. More specifically, for example, a digimaticindicator 85 is provided on the mount 41, which constitutes aparallelism measuring means for measuring the parallelism of the currentplate 5 as shown in FIG. 22. The raising and lowering mechanism 65raises and lowers the current plate 5 through the raising and loweringplate 53 a and the support rods 51 while receiving the detection valueof the digimatic indicator 85, so that the current plate 5 is adjustedto be parallel to the wafer W. In this case, the current plate 5 can beaccurately aligned to be parallel to the wafer W, thereby forming thecoating film with more uniform film thickness.

Next, still another example of the reduced-pressure drying unit 26 ofthe present invention is explained with reference to FIG. 23. Thisexample has a configuration that, in place of the current plate 5 in theshape of a plate, a current member 86 is provided which is formed in theshape of an inverted U to surround the front face and the outer edge ofthe wafer W. This current member 86 has a substantially horizontal plane86 a which is formed to face the front face of the wafer W and asubstantially vertical plane 86 b which extends downward substantiallyin the vertical direction from the horizontal plane 86 a in a region inthe outer vicinity of the wafer W to cover the outer edge of the waferwhile forming a slight gap with the outer edge. The substantiallyhorizontal plane 86 a is formed with many ventilation holes 86 c atregular intervals in the circumferential direction in a region in thevicinity of the outer periphery of the wafer. The gap between the sideface of the wafer W and the substantially vertical plane 86 b is set,for example, about 0.1 mm to create a large loss in pressure here.

In this example, for example, the diameter of a mount 87 for mounting awafer thereon is set almost the same size as that of the wafer W, andthe substantially vertical plane 86 b extends to a position beside themount 87 under the wafer W to cover the side face of the mount 87through a slight gap. The gap between the side face of the wafer W andthe side face of the mount 87 and the substantially vertical plane 86 bis set, for example, about 0.1 mm to create a large loss in pressurehere. In this example, a hermetic container 4A is constituted by the lidbody 42 and a lower container 88, and the mount 87 is disposed insidethe lower container 88.

In such a configuration, when the hermetic container 4A is made into areduced-pressure atmosphere, the exhaust current in the container 4A isformed to detour the current member 86, so that solvent vapor vaporizingfrom the wafer W hits against the current member 86 to change indirection outward and flows along the inner side of the current member86. Since just a slight gap is formed between the outer edge of thewafer and the side face of the mount 87 and the current member 86, alarge loss in pressure is generated here. Therefore, the solvent vaporvaporizing from the wafer W flows from the ventilation holes 86 c towardthe exhaust pipe 45, thereby forming a stable air current whichuniformly spreads in the radial direction. The solvent vapor uniformlyspreads out in the radial direction as described above, thereby furtherimproving the film thickness at the peripheral region of the coatingfilm to further increase uniformity of the film thickness.

In this event, as shown in FIG. 24, for example, a second current plate89 may be provided above the current member 86 in the hermetic container4A while facing the substantially horizontal plane 86 a of the currentmember 86 to vertically divide the lid body 42, and ventilation holes 89a may be formed in the second current plate 89 at positionscorresponding to the outer periphery and its vicinity of the wafer W. Inthe configuration in FIG. 24, the ventilation holes 86 c of the currentmember 86 are formed in the substantially vertical plane 86 b in thevicinity of the outer periphery of the wafer W.

In such a configuration, when the inside of the hermetic container 4A ismade into a reduced pressure atmosphere, the solvent vapor vaporizingfrom the wafer W flows out from the ventilation holes 86 c toward theexhaust pipe 45 and through the ventilation holes 89 a formed in thesecond current plate 89 toward the exhaust pipe 45. Such a doublestructure of the current member 86 and the second current plate 89enables the formation of a stable air current which uniformly spreadsout in the radial direction of the wafer W. Thereby, the solvent vapormore uniformly spreads out in the radial direction so that the filmthickness of the coating film can be further improved at the peripheralregion of the coating film to further increase the uniformity of thefilm thickness.

It should be noted that the current member 86 and the second currentplate 89 are also applicable to the case in which the wafer is mountedon the mount 41 having the configuration in FIG. 6, and in this case,the substantially vertical plane 86 b is constituted to extend to aposition covering the side of the wafer W through a slight gap, therebyimproving the film thickness at the peripheral region of the coatingfilm formed on the front face of the wafer W.

Further, the reduced-pressure drying unit 26 may be configured as shownin FIG. 25. This embodiment is constituted such that, adjacent to ahermetic container 9A in which the reduced-pressure drying processing isperformed, a transfer chamber 9B is provided which includes a subsidiarycarrier 91 dedicated to carry the wafer W to the hermetic container 9A,and that a gate valve 90 opens and closes between the hermetic container9A and the transfer chamber 9B.

The subsidiary carrier 91 delivers and receives the wafer W to/from thealready-described main carrier 24, in which, for example, as shown inFIG. 25, two arms 91 a are configured to freely approach and retractto/from the hermetic container 9A and to be ascendable and descendableseparately. Further, the transfer chamber 9B is provided with a deliverytable 92 including delivery pins 92 a which are ascendable anddescendable by a raising and lowering mechanism 92 b for delivering andreceiving the wafer between the subsidiary carrier 91 and the maincarrier 24. This delivery table 92 is configured such that, for example,as shown in FIG. 26, the arm 91 a of the subsidiary carrier 91 and thearm of the main carrier 24 can access each other in such a manner not tointerfere with the delivery pins 92 a, so that the wafer can bedelivered and received between them. Numeral 93 a in FIG. 26 denotes amount of the wafer W and numeral 93 b denotes an exhaust pipe.

In such a configuration, the wafer W is carried in the transfer chamber9B by the main carrier 24 through a not shown wafer transfer port of thetransfer chamber 9B with the gate valve 90 closed, and the wafer W isdelivered to the subsidiary carrier 91 via the delivery pins 92 a. Afterthe main carrier 24 is allowed to retract out, the transfer port isclosed, and thereafter the gate valve 90 is opened to allow thesubsidiary carrier 91 to carry the wafer W into the hermetic container9A.

In this embodiment, the wafer W is first carried to the transfer chamber9B, then the transfer chamber 9B is closed, and the gate valve 90 isopened to carry the wafer W into the hermetic container 9A, therebypreventing the external air from entering the container 9A when thewafer W is carried into the hermetic container 9A.

Further, in the reduced-pressure drying unit 26, for example, as shownin FIG. 27, a part of the side wall of the hermetic container 9A may beconstituted by a transparent element 94 made of, for example,transparent vinyl chloride. For example, the transparent element 94 isattached to a side wall 95 a through an O-ring 95 c to close an opening95 b which is formed in the side wall 95 a of the hermetic container 9A.This arrangement has an advantage that the reduced-pressure dryingprocessing performed in the hermetic container 9A can be confirmed by avisual check.

The reduced-pressure drying unit 26 is installed, for example, in theshelf units U2 and U3, in which case, the carriage of the wafer W intothe reduced-pressure drying unit 26 and the carriage of the wafer W fromthe reduced-pressure drying unit 26 are performed by the delivery arm23, the main carrier 24, and the carrier arm 27 in predeterminedprocesses.

In consideration of convenience for these carrier devices to access theinside of the reduced-pressure drying unit 26 in the above case, forexample, a reduced-pressure drying unit 26 shown in FIG. 28 can beproposed. Specifically, in the reduced-pressure drying unit 26 shown inFIG. 28, openings 101 and 102 are provided on respective sides of thetransfer chamber 9B. Therefore, the above-described carrier devices cancarry the wafer W into/out of the reduced-pressure drying unit 26through the openings 101 and 102.

It should be noted that while the above-described mount 41 has aconfiguration including the heater H therein, it is also adoptable touse a mount 112, as shown in FIG. 29, having a temperature regulator,for example, Peltier elements 111.

The mount 112 has a face plate 113 on the front face where a substratesuch as a wafer or the like is directly mounted. The face plate 113 isattached to the body of the mount 112 through a sealing material 114such as an O-ring in consideration of air tightness. Under the lowerface of the face plate 113, the Peltier elements 111 are arrangedannularly and concentrically. Under the Peltier elements 111, a coolingflow passage 115 is provided for cooling the lower face side of thePeltier elements 111. Through the cooling flow passage 115, for example,a cooling fluid such as cooling water or the like flows. The coolingfluid circulates between a cooling fluid supply source (not shown) andthe cooling flow passage 115 through a flow passage 116.

According to the mount 112 having the above-described configuration, thesubstrate such as a wafer or the like mounted on the face plate 113 canbe regulated in temperature within a range, for example, from 10° C. to40° C. Therefore, the use of this mount 112 makes it possible to keepthe temperature of the wafer at a low temperature, for example, at about15° C. at the beginning during the reduced-pressure drying to preventthe solvent from vaporizing from the coating solution such as a resistsolution or the like on the wafer, and thereafter to keep thetemperature of the wafer at room temperature, for example, at 23° C.when drying the wafer, for example, with the current plate made closerto the wafer to control the liquid flow of the coating solution, so thatthe drying processing can appropriately be performed.

The substrate used in the present invention in the above explanation maybe an LCD substrate or a reticle substrate for a photomask. Further, thecoating solution is not limited to the resist solution, but may be aninterlayer insulating material, a low dielectric material, aferroelectric material, a wiring material, an organic metal material, ametal paste, or the like. Further, the present invention is applicableto an application of the coating solution by a spin coating method, andalso to an application of the coating solution by supplying the coatingsolution onto the front face of the substrate in a spiral form.

As described above, according to the present invention, areduced-pressure drying processing can be performed keeping a highuniformity of film thickness of a coating film in a reduced-pressuredrying unit for a substrate used in forming a coating film.

What is claimed is:
 1. A reduced-pressure drying unit for a substrate,comprising: a hermetic container provided therein with a mount formounting thereon a substrate coated with a coating solution made bymixing a component of a coating film and a solvent; a vacuum exhausterconnected to said hermetic container through an exhaust passage forreducing a pressure in said hermetic container to vaporize the solventfrom the coating solution on the substrate; a pressure sensor fordetecting the pressure in said hermetic container; a current memberprovided to face a front face of the substrate mounted on said mount;and a current member raising and lowering mechanism for raising andlowering said current member, wherein said current member is raised andlowered by said current member raising and lowering mechanism to changein height position while the pressure inside said hermetic container isreduced to vaporize the solvent from the coating solution on thesubstrate, said current member is changed from a first position to asecond position while the solvent is vaporizing from the coatingsolution on the substrate, and, when a detection value from saidpressure sensor becomes a predetermined pressure or lower, the heightposition of said current member is changed from the first position tothe second position.
 2. A reduced-pressure drying unit as set forth inclaim 1, further comprising: a film thickness measuring sensor formeasuring a thickness of the coating film formed on the front face ofthe substrate, wherein the height position of said current member ischanged based on a measurement value from said film thickness measuringsensor.
 3. A reduced-pressure drying unit as set forth in claim 2,further comprising: a pressure adjuster provided between said exhaustpassage and said vacuum exhauster for adjusting a displacement, whereina displacement in said hermetic container is controlled by said pressureadjuster based on the measurement value from said film thicknessmeasuring sensor to control a vaporization period of the solvent.
 4. Areduced-pressure drying unit as set forth in claim 1, wherein saidcurrent member is composed of an element in a shape of a plate.
 5. Areduced-pressure drying unit as set forth in claim 1, wherein saidcurrent member has a form covering the front face and an outer edge ofthe substrate.
 6. A reduced-pressure drying unit for a substrate,comprising: a hermetic container provided therein with a mount formounting thereon a substrate coated with a coating solution made bymixing a component of a coating film and a solvent; a vacuum exhausterconnected to said hermetic container through an exhaust passage forreducing a pressure in said hermetic container to vaporize the solventfrom the coating solution on the substrate; a heater in said hermeticcontainer for heating the substrate; a current member provided to face afront face of the substrate mounted on said mount; and a current memberraising and lowering mechanism for raising and lowering said currentmember, wherein said current member is raised and lowered by saidcurrent member raising and lowering mechanism to change in heightposition while the pressure inside said hermetic container is reduced tovaporize the solvent from the coating solution on the substrate, thesubstrate is heated by said heater while the solvent and/or water are/isvaporizing from the coating solution on the substrate so that thesolvent and/or water vaporize/vaporizes, and a pressure in said hermeticcontainer and/or a film thickness of the coating solution on thesubstrate are/is detected so that the heating by said heater isperformed based on the detection values/value.
 7. A reduced-pressuredrying unit as set forth in claim 6, wherein the reduction in pressurein said hermetic container by said vacuum exhauster is stopped while thesubstrate is being heated by said heater.
 8. A reduced-pressure dryingunit as set forth in claim 6, wherein said heater for heating thesubstrate is provided in said current member.
 9. A reduced-pressuredrying unit for a substrate, comprising; a hermetic container providedtherein with a mount for mounting thereon a substrate coated with acoating solution made by mixing a component of a coating film and asolvent; a vacuum exhauster connected to said hermetic container throughan exhaust passage for reducing a pressure in said hermetic container tovaporize the solvent from the coating solution on the substrate; acurrent member provided to face a front face of the substrate mounted onsaid mount; a current member raising and lowering mechanism for raisingand lowering said current member, said raising and lowering mechanismbeing provided on a rear face side of said current member for pushingsaid current member to change the height position of said currentmember; and a hang-supporter connected to a front face of said currentmember for attaching said current member to a lid body of said hermeticcontainer, wherein said current member is raised and lowered by saidcurrent member raising and lowering mechanism to change in heightposition while the pressure inside said hermetic container is reduced tovaporize the solvent from the coating solution on the substrate, saidcurrent member is hung by means of said hang-supporter to be movable ina vertical direction, said current member and said hang-supporter areconnected to each other with a spherical joint, said current memberraising and lowering mechanism has a raising and lowering rod having aventilation hole therein, and one end of said raising and lowering rodis in contact with the rear face of said current member and another endof said raising and lowering rod is connected to an exhauster.
 10. Areduced-pressure drving unit for a substrate, comprising: a hermeticcontainer provided therein with a mount for mounting thereon a substratecoated with a coating solution made by mixing a component of a coatingfilm and a solvent; a vacuum exhauster connected to said hermeticcontainer through an exhaust passage for reducing a pressure in saidhermetic container to vaporize the solvent from the coating solution onthe substrate; a current member provided to face a front face of thesubstrate mounted on said mount; a current member raising and loweringmechanism for raising and lowering said current member, and a secondcurrent member at a position closer to said exhaust passage than saidcurrent member in said hermetic container, said second current platehaving ventilation holes at positions corresponding to the vicinity ofthe outer periphery of the substrate, wherein said current member israised and lowered by said current member raising and lowering mechanismto change in height position while the pressure inside said hermeticcontainer is reduced to vaporize the solvent from the coating solutionon the substrate.
 11. A reduced-pressure drying unit for a substrate,comprising: a hermetic container provided therein with a mount formounting thereon a substrate coated with a coating solution made bymixing a component of a coating film and a solvent; a vacuum exhausterconnected to said hermetic container through an exhaust passage forreducing a pressure in said hermetic container to vaporize the solventfrom the coating solution on the substrate; and a plurality of aligningmembers provided at positions outside said mount and apart from a centerposition of said mount by equal distances in radial directions, whereinsaid plurality of aligning members synchronously move in substantiallyhorizontal directions from the positions outside the substrate topositions to come into contact with an edge of the substrate to alignthe center position of said mount and a center position of thesubstrate.